Exemplary embodiments of the invention relate to a single-actuation valve arrangement, particularly for an aerospace component. It comprises an inlet and an outlet as well as an actuator that can be actuated by a heating element. In a non-actuated state of the actuator, flow throughput is enabled between the inlet and the outlet. The valve arrangement thus constitutes a so-called normally-open (NO) configuration. The invention further relates to an aerospace component.
Valves are generally used, for example, in places in which a pipe for liquid or gaseous media needs to be opened or closed. Depending on the application, the valves can be provided for multiple or also only one-time actuation, the latter being the case in drive systems for aerospace applications, for example.
Valves for orbital drive systems are often actuated by pyrotechnical means. While the service life of satellites is becoming longer and longer and can already be more than 15 years, the service life of a pyrotechnical actuator is limited to a few years. If a pyrotechnical valve is actuated at the beginning of a mission, this poses no problem. However, if a valve is to be actuated toward the end of the planned service life of a satellite, for example in order to discharge containers, then the actuation of the valve must be achieved in another way, since the function of the pyrotechnical components cannot be safely ensured.
Another drawback, particularly of pyrotechnical actuators, is that single-use valves are often actuated very quickly, and hydraulic and/or structural shock loads can result.
In general, high demands are placed on the reliability of the control of valves in aerospace applications, since a malfunction could lead to substantial damage to or even the loss of the drive system.
Exemplary embodiments of the present invention are directed to a structurally and/or functionally reliable valve arrangement for closing a valve as well as a corresponding aerospace component for aerospace applications.
Exemplary embodiments of the present invention provide a valve arrangement, particularly for an aerospace component, for one-time actuation, which comprises an inlet and an outlet as well as an actuator that can be actuated by a heating element. In a non-actuated state of the actuator, flow throughput is enabled between the inlet and the outlet. This corresponds to a so-called normally-open (NO) configuration. The actuator is a single-use effect shape memory actuator that is compressed in the martensitic state along a longitudinal axis of the actuator and is integrated into the valve arrangement. Through the activation of the heating element upon reaching a predetermined transformation temperature, the single-use effect shape memory actuator undergoes a change in length, whereby it is gradually pressed against a seal seat that is embodied at the inlet or the outlet.
The invention provides a valve arrangement that can be used independently of the service life of an aerospace component, even toward the end of it. A high level of reliability is ensured by the principle employed. To close the valve that is open before actuation, the valve is electrically heated. Upon reaching the transformation temperature, the actuator expands until the original length before compression is reached. Such great forces are thus released that a high-level sealing effect is achieved through the pressing of the single-use effect shape memory actuator against the seal seat. Upon cooling of the actuator, its length and force on the seal then remain intact, whereby the valve remains permanently closed.
The principle underlying the valve arrangement is not subject to any limitation in terms of service life. This results particularly from the fact that the valve arrangement does not use stored chemical energy of any kind. Another advantage is that the valve arrangement can be actuated slowly. As a result, hydraulic shock loads (so-called “water hammer”) can be avoided. Likewise, as a result, no structural shock loads occur as a result of the triggering of explosive charges like in a pyrotechnical valve.
According to an advantageous embodiment, the transformation temperature of the material of the actuator lies between 80° C. and 100° C. In general, the transformation temperature depends on the material of the single-use effect shape memory actuator. For example, a nickel-titanium alloy can be used which is also known by the name of Nitinol.
According to another exemplary embodiment, a sealing piston is arranged on a front side of the actuator facing away from the seal seat. The sealing piston can be made of a ductile material. In consideration of the long-term compatibility of the media to be conveyed, PTFE, aluminum alloys or gold-plated austenitic chromium-nickel steel can be used, for example. Furthermore, it is advantageous if the sealing piston is embodied in the shape of a truncated cone. The sealing effect can be positively influenced in the desired manner through the material and the structure of the sealing piston.
Furthermore, it is advantageous if the seal seat has a truncated-cone shape corresponding to the shape of the sealing piston. The seal seat can be made of a material that is harder in comparison to the scaling piston. This ensures that, as the single-use effect shape memory actuator expands and the great pressures thus released upon pressing against the seal seat, a plastic deformation of the ductile occurs and the desired high-level sealing effect is achieved.
According to another exemplary embodiment, an interior space of the housing is subdivided by an elastic partition element into a working space and a free space. The inlet and the outlet advantageously lead into the working space, a first longitudinal segment of the actuator being arranged in the working space with respect to the quantity of the longitudinal actuator. A provision is also made that, with respect to the length of the longitudinal actuator, a second longitudinal segment is arranged in the free space that is larger or substantially larger than the first longitudinal segment. An optional separation of media can be achieved in this way. This is advantageous, for example, if the material of the shape memory actuator and the medium to be connected (e.g., a gas or a fluid) are not chemically compatible.
The partition element can be a metal bellows or a diaphragm. In principle, the material of the partition element is selected such that there is compatibility with the medium to be connected. A titanium or an FeNiCr alloy, for example, can be used as the material.
In another embodiment, the actuator has a recess extending in the direction of the longitudinal axis in whose interior the heating element is arranged. The recess can be embodied, for example, as a bore and pass substantially nearly completely through the actuator.
In order to ensure the switching-off of the heating element, it is advantageous for the heating element to be secured by means of a thermal fuse. When the transformation temperature is exceeded, the thermal fuse can be tripped, thus separating the power circuit from the heating element. Overheating of the medium to be connected can be prevented in this way.
According to another embodiment, the longitudinal axis of the actuator matches with a longitudinal axis of the inlet or of the outlet. For example, the inlet and the outlet can be arranged on different sides of a housing of the valve arrangement. For example, the a be arranged on the bottom of the housing, while the inlet is provided on one of the side walls of the housing of the valve arrangement. This enables not only a simple construction, but also the abovernentioned separation of media with the aid of the partition element. It is advantageous in this context if the inlet is then arranged in the vicinity of the bottom so that the shape memory actuator has as little co act as possible with the medium to be connected, i.e., the first longitudinal segment can be kept as short as possible.
Furthermore, an aerospace component for an aerospace application is provided, which has at least one valve arrangement of the type described above. The aerospace component, e.g., a satellite, a drive component or the like, has the same advantages as were described above in connection with the valve arrangement according to the invention.